According to the World Health Organization (WHO), more than one-third of the world's population, approximately 2 billion people, is infested with helminths. In 1999, the WHO estimated that schistosomiasis and soil-based helminths represented more than 40% of the disease burden due to all tropical disease, excluding malaria. While most parasitic infestations are preventable and treatable, the effects of an infestation can be chronic and long-term and may eventually cause death. For example, a person who has endured persistent and heavy infestations is likely to suffer from anemia, malnutrition and chronic irreversible diseases, such as liver fibrosis, cancer of the bladder and kidney failure. These parasites also affect livestock, which can facilitate infestation in humans by causing contamination via soil or food supplies.
In addition to the health risk posed to humans by parasites, plants are highly susceptible to parasitic infestations. Effects of nematode damage to plants include stunting, chlorosis, nutrient deficiencies, wilting, root abnormalities and reduced yield.
While there are a number of antihelminthic treatments currently available, some scientists are concerned that the parasites will develop resistance to these treatments, especially in developing countries where people are repeatedly infected with helminths and receive multiple doses of antihelminthic drugs. In fact, resistance to antihelminthic drugs has been observed in livestock due to frequent and repeated treatments. Moreover, rates of re-infection by helminths are very high due to the number and the durability of infective eggs on surfaces and in soil. While infection is active, some parasitic nematode species (e.g., Ascaris lumbricoides) release an estimated 100,000 new embryos per adult female per day. Currently available anti-helminthics work by paralyzing the infectious nematode through blocking ion channels and receptors and do not inactivate the embryos that cause re-infection. Therefore, it is advantageous to develop new therapies for the treatment and prevention of parasitic infestations and, in particular, therapies that limit the possibility of parasitic re-infection, in both plants and animals,